Currently, some hydraulic devices such as shock absorbers comprise two parts assembled together.
The first part comprises a piston-rod assembly, and the second part comprises a housing that features a tube cylindrical enough to allow a piston-rod assembly to slide inside it in the presence of hydraulic fluid.
This assembly allows to decouple the joint movement of the assembly to the tubular housing from the joint movement of the assembly to the piston-rod assembly, so that hydraulics are able to filter, either partially or totally, the frequencies that want to be prevented from transmitting from one assembly to the other.
Based on the geometric limitations of the physical environment where the shock absorber operates, the maximum distance the piston can travel inside the housing (the stroke of the shock absorber) is limited. In certain devices, said limitations are implemented by means of mechanical stops:                When the minimum length of the shock absorber is limited, these stops are known as compression stops, maximum compression stops, etc.        When the maximum length of the shock absorber is limited, these stops are known as rebound stops, maximum extension stops, etc.        
In some applications of the shock absorber, the relative abruptness of these mechanical stopping devices can be undesirable due to lack of comfort, excessive noise, wearing out due to continued use, etc.